Powers:When Theo Adam says the magic word "Shazam" and is transformed into Black Adam, he is granted the following powers (which are derived not from the same Greco/Roman/Biblical figures as Captain Marvel, but from more ancient Egyptian gods):
S for the stamina of Shu Using Shu's endurance, Black Adam can withstand and survive most types of extreme physical assaults. Additionally, he does not need to eat or breathe and can survive unaided in space.
H for the swiftness of Heru By channeling Heru's speed, Black Adam can fly and steadily run at a top speed of Mach 500.
A for the strength of Amon Black Adam has a phenomenal level of super strength, able to easily bend steel, punch through walls and lift massive objects. Adam's strength is enough that he can hold his own against beings such as Superman or Captain Marvel.
Z for the wisdom of Zehuti Black Adam has instant access to a vast level of scholarly knowledge. The wisdom of Zehuti also gives Adam clairvoyance and provides him with counsel and advice in times of need.
A for the power of Aton Aton's power, besides fueling the magic thunderbolt that transforms Adam, also enhances Adam's other physical abilities and allows for inter dimensional travel. Adam can use the lightning bolt as a weapon by dodging it and allowing it to strike an opponent or target. (In his earliest appearance he could project lightning directly.)
M for the courage of Mehen This aspect is partly psychological, and gives Adam superhuman amounts of inner strength to draw off of, while also making him indestructible to harm like the great snake itself.

Additionally, Adam's senses are acutely sharpened (though not to the extent of Superman's).

Saying the magic word again will change Black Adam back into Theo Adam. However, Black Adam very rarely changes back to his non-powered form. Also, as Captain Marvel shares his powers with the rest of the Marvel Family, Adam's unshared powers are often depicted as rendering him somewhat stronger than the Captain.

Bio:In this revised origin (told in Power of Shazam! #10), Teth-Adam was the son of the ancient Egyptian Pharaoh Rameses II, and impressed one of the high priests, the wizard Shazam, with his good deeds. The wizard had the young prince brought before him, and ordered him to speak his name. Teth-Adam did so, and was transformed into Mighty-Adam, a superhero possessing the stamina of Shu, the swiftness of Heru (Horus), the strength of Amon, the wisdom of Zehuti, the power of Aton, and the courage of Mehen.

Mighty-Adam served as Egypt's champion for many centuries, but became corrupted by the charms of a mysterious woman, revealed to be Shazam's evil daughter Blaze in disguise. Bewitched by Blaze, Adam became convinced that he and his mistress should rule the Egyptian kingdom, so he killed the Pharaoh and appointed himself ruler. Shazam was made aware of this treachery and, as a result, unleashed a powerful spell on Adam. The wizard extracted Mighty Adam's magic powers and encased them in a mystical scarab necklace, rendering Adam's de-powered body, now several hundred years old, into a withered corpse.

Shazam then buried both the body and the scarab in the tomb of Rameses II, where he had planned for it to remain for all eternity. In death, the former hero was referred to as "Khem-Adam" ("Black Adam"). Disillusioned by what he perceived as Adam's betrayal, Shazam went several millennia before appointing a second champion to fight evil in his name.

The original Power of Shazam! graphic novel (which predated the publication of the series by a year) explained how Black Adam was revived and introduced into the modern world. In this story, an unscrupulous archaeological aide named Theo Adam finds himself assigned to the Malcom Expedition, an archaeological dig financed by the Sivana Foundation to excavate the tomb of Rameses II. Adam uncovers Khem-Adam's tomb in a secret passageway, and leads his superiors, C.C. Batson and his wife Marilyn, to the discovery. Upon first sight of Khem-Adam's scarab, Theo Adam became obsessed with the artifact, and killed both Batsons in order to steal it. Escaping Egypt, Theo Adam soon made his way back to America.

The Batsons' son, Billy, had been left behind in the United States, and was soon appointed to become Captain Marvel, the second champion of the wizard Shazam. When Theo Adam first encountered Captain Marvel, he noted both Marvel's identical appearance to C.C. Batson and the lightning-bolt insignia on Marvel's chest that had also decorated Khem-Adam's tomb. Adam therefore had a revelation, and realized that he was a reincarnation of Khem-Adam. Grasping his stolen scarab, Adam spoke the wizard's Shazam's name and was transformed into the super-powered Black Adam. Black Adam revealed himself to Captain Marvel as the Batsons' killer, and the two battled. Captain Marvel emerged victorious by snatching Adam's scarab, and therefore his power, away from him. Marvel brought Theo Adam to Shazam, who wiped Adam's memory and took away his voice, so that he could not access his powers.

#15 - 'The Good Fight'#16 - 'One World, Under Gog, Part 1: He Came, and Salvation with Him'#19 - 'One World, Under Gog, Part IV: Out Of Place'#23 - 'Between a Rock and a Hard Place, Part One: The Power of Shazam'#24 - 'Black Adam & Isis Part Two: Family Ties'#25 - 'Black Adam & Isis Part Three: Family Feuds'

Infinite Crisis Special - 'A Hero Dies But One'#1 - 'Villains United, Part One: And Empires in Their Purpose'#2 - 'Villains United, Part Two: A Fire in the Steppes'#3 - 'Villains United, Part Three: Privileged to Spill Her Blood'#4 - 'Villains United, Part Four: A Weapon to Unify'#5 - 'Villains United, Part Five: Victims of Aggression'#6 - 'Villains United, Part Six: At the End of All Things'